He might be...
Apart from being a little gruesome looking, what symptoms does he have? He probably has an illness. If you want to, take him to a vet.
I know what you're going through- I ha a calico goldfish named Flake, one day he got trapped by the filter. I let him out but he had a major lack of oxygen and was convulsing. I had to go to violin and on the way back I got a text from my parents saying he was gone... very sad.
P.S. I hope that your fish will be OK. It might be just a fish but when you care for it like Flake, you get rather attached to seeing it swim around.
R.I.P. Flake
